K.F. Ng-Kwai-Hang

Correlations Between Coagulation Properties of Milk and Cheese Yielding Capacity and Cheese Composition

Abstract On a monthly basis, approximately 4 L of milk were collected from each of 53 Holstein cows during the morning milking for one entire lactation. Subsamples of milk were analyzed by a forma-graph for coagulating properties which were expressed as rennet clotting time, rate of firming and curd firmness. Cheese yielding capacity, gross composition of resulting cheese, and losses of milk components in the whey were also determined. Partial correlation coefficients between coagulating properties and cheese yield, cheese composition and milk components in whey were calculated. All three formagraphic parameters were correlated (p

Acid coagulation of skimmilk powder by extrusion processing

Abstract Using the extruder as a continuous reactor, skimmilk powder was mixed with acid to produce an acid-coagulated product. The extrusion process was studied by response surface methodology to determine the influence of the extrusion parameters on selected extrudate physico-chemical responses including total and soluble protein, non protein nitrogen (NPN), lactose, and pH. Analysis of the high heat skimmilk powder extrudates showed that total and soluble protein, NPN and lactose were not affected by any of the extrusion parameters, while pH was significantly affected by moisture and screw speed. When medium heat skimmilk powder was used, total protein and lactose levels were significantly affected by temperature. The final pH values of extrudates from both powders were significantly affected by moisture or acid level, however polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulphate(SDS)-PAGE electrophoresis of the extruded product did not show any alteration in the caseins of the original skimmilk powders. Extrusion processing appears to be a potential means of preparing an acid-coagulated product from skimmilk powder as a preliminary step to the production of sodium caseinate.